Renewable fuse



J. L. FAY. I

.RENEWABLE FUSE. APPLICATION HLEI) MAY 16, 1919.

1,428,768. I PatentedSept-L 12, 1922.

Patented Sept. 12, 1922.

UNITED STATES PATENT OFFICE.

JOHN L. FAY, OF ST. LOUIS, MISSOURI, ASSIGNOB OF ONE-HALF '10 WARD S. IRELAND,

\ OF ST. LOUIS, MISSOURI.

RENEWABLE EusE.

Application filed May 16 To all whom it may concern:

Be it known that I, JOHN L. FAY, a citizen of the United States, and a resident of the city of St. Louis, in the State of Missouri, have invented certain new and useful Improvements in Renewable Fuses, of which the followin is a full, clear, and exact description, re erence being had to the accompanying drawings, forming a part of this specification.

My invention relates to that type of fuses intended to be used repeatedly upon the replacement of burned out fuse elements the object being to provide a simple means for preventing the use of a relatively wide fuse element through which an overload may be conducted.

Fig. I is a side elevation of my renewable fuse.

Fig. II is a longitudinal section on an irregular line.

Fig. III is an end elevation.

Fig. IV is a cross section taken on line IV-IV Fig. II.

Fig. V is a cross section taken on line VV Fig. II.

Fig. VI is a cross section on line VI-VI, Fig. II.

' Fig. VII is a side elevation of the fuse element and terminal stems removed from the casing.

Fig. VIII is a longitudinal section taken on a line approximately at a right angle to the line on which the section shown in Fig. 111 is taken. I

In the drawings, 1 designates the shell and 2 the ferrules or end caps of the casing of my fuse, the latter being removably secured to the shell and being provided at their outer ends with inturned flanges 3.

' A designates the fuse strip or fuse element of my renewable fuse and B the terminal stems to which the ends of said fuse element are secured by bolts 7 or other fasteningmeans.

The fuse element A comprises head portions 4 and a reduced central portion 5 between said head portions, the latter being a straight imperforate member designed to withstand less heat than the end portions of the fuse element, so that it will melt in the burning out of the fuse.

Upon the reduced portion 5 ofthe fuse element A, I place an enclosing member 6,

, 1919. Serial No. 297,608.

which serves to concentrate and hold heat thereln for the melting of the fuse element. This enclosing member is preferably of plaster of Paris or other suitable cement, and is molded around the fuse element throughout any dsired ortion of the reduced central portion of said element. When an electrical current of sufficient strength to melt the central imperforate portion of the fuse element enters into said central portion, the resultant heat is concentrated within the enclosing member 6 due to the enclosing member holding the heat and preventing, radiation into the air within the fuse casing, and the fuse element is therefore melted within said enclosing member instead of aside therefrom. The melting or burning out of the fuse within the enclosing member 6 is aided by spread -of heat into the increased area of the ends of the fuse element, and the terminal stem into which the heat produced by the strong electrical current is partially absorbed, the increased area of the parts aside from said reduced portion conducting the heat away from the reduced central portion of the fuse element, at the same time that the enclosing member 6 is storing heat units therein to cause the fuse element to melt within said enclosing member. It will be apparent that by confining the heat of sufiicient degree to melt the fuse within the enclosing member 6, the point at which the fuse is melted will be definitely within said enclosing member, and that said enclosing member serves to prevent the formation of arcs within the fuse casing and also acts as a barrier to avoid injury .to the casing when the fuse element is burned out. The terminal stems B are preferably formed from pieces of sheet metal folded to form two layers. These layers are slit longitudinally at the inner ends of each stem, and the marginal portions of the stem adjacent the slits are bent laterally and backwardly to provide opposing pairs of outturned, lips 8 between which the heads of the fuse element are interposed. Said lips-therefore constitute abutments or shoulders which are spaced apart a distance not reater than the widths of the heads of the use element intended to be used in a articular renewable fuse. Therefore said ips limit the size of a fuse element which may be attached to v the terminal stems of my fuse, and prevent the use of a wider fuse element through which an overload of electrical current might be carried.

Each terminal stem B is retained in position in the casing of my fuse by a pair of detent plates 9 at the ends of the casing shell 1, said plates being confined by the in turned flanges 3 of the ferrules 2. The detent plates are located at opposite sides of the terminal stems B with their outer margins seated on the ends of the casing shell, and they are provided at their inner margins with wings 10 which extend into the casing so as to lie against the sides of the terminal stems, as seen in Figs. 11 and VIII, and centralize said stems. Each detent plate is provided at its inner margin with a tongue 11 shown most clearly in Fig. V, the tongues of each pair of plates being so disposed that they will overlap each other. Said tongues extend into apertures 12 in the terminal stems whereby the detent plates are interlocked with the terminal-stems to hold the latter in the fuse casing. Between the detent plates 9 and the inturned flanges of the ferrules 2 are closure disks 13 provided with central openings closely fitted to the terminal stems, and serving to close the gaps between the detent plates and the terminal stems of the fuse.

The apertures 12 in the terminal stems into which the detaining tongues of the detent plates 9 extend are longer than the thickness of said detaining tongues 11, as most clearly seen in Fig. VIII, being so formed with specific objects in view, viz., to permit longitudinal movement of the terminal stems relative to the casing of the fuse while thefuse is closed, thereby making it possible to determine whether or not the fuse element A connecting the terminal stems is intact or not, without opening the fuse casing, determination of such fact being made by moving either ofthe terminal stems longitudinally as permitted by the play provided, due to the length of the apertures 12 being greater than the thickness of the detaining tongues 11. If the fuse element is intact the movement of either terminal stem will be indicated by movement of the other terminal stem, whereas if the fuse element is burned out or broken, movement imparted to either terminal stem will not be communicated to the other terminal stem. Further, by making the apertures 12 longer than the thickness of the detaining tongues 11, I provide for ready unseating of the detent plates from the cas ing shell, when the casing is opened in the" event of the separable members at the ends of the casings having become adhered to the casing shell.

I claim:

1. A renewable fuse comprising a fuse element, terminal stems, and fastening means whereby the end portions of the fuse element are detachably secured to said terminal stems, the end margin of each terminal stem being provided with opposing pairs of outturned lips to provide abutments for limiting the width of the fuse element applicable to the stem, said abutment lips having oppositely disposed side edges adapted to engage the side edges of the fuse element.

2. A renewable fuse comprising a fuse element, and terminal stems to which the ends of said fuse element are detachably secured, each of said terminal stems comprising a folded piece of sheet metal, each fold having longitudinal slits in its fuse-receiw ing end providing pairs of spaced lips, and said lips being extended laterally at the side margins of said terminal stem so as to lie at opposite sides of said fuse element.

In testimony that I claim the foregoing I hereunto aflix my signature.

JOHN L. FAY. 

